Sviluppo di biosensori: modifiche di superfici elettrodiche e sistemi di immobilizzazione enzimatica

An amperometric glucose biosensor was developed using an anionic clay matrix (LDH) as enzyme support. The enzyme glucose oxidase (GOx) was immobilized on a layered double hydroxide Ni/Al-NO3 LDH during the electrosynthesis, which was followed by crosslinking with glutaraldehyde (GA) vapours or with GA and bovine serum albumin (GABSA) to avoid the enzyme release. The electrochemical reaction was carried out potentiostatically, at -0.9V vs. SCE, using a rotating disc Pt electrode to assure homogeneity of the electrodeposition suspension, containing GOx, Ni(NO3)2 and Al(NO3)3 in 0.3 M KNO3. The mechanism responsible of the LDH electrodeposition involves the precipitation of the LDH due to the increase of pH at the surface of the electrode, following the cathodic reduction of nitrates. The Pt surface modified with the Ni/Al-NO3 LDH shows a much reduced noise, giving rise to a better signal to noise ratio for the currents relative to H2O2 oxidation, and a linear range for H2O2 determination wider than the one observed for bare Pt electrodes. We pointed out the performances of the biosensor in terms of sensitivity to glucose, calculated from the slope of the linear part of the calibration curve for enzimatically produced H2O2; the sensitivity was dependent on parameters related to the electrodeposition in addition to working conditions. In order to optimise the glucose biosensor performances, with a reduced number of experimental runs, we applied an experimental design. A first screening was performed considering the following variables: deposition time (30 - 120 s), enzyme concentration (0.5 - 3.0 mg/mL), Ni/Al molar ratio (3:1 or 2:1) of the electrodeposition solution at a total metals concentration of 0.03 M and pH of the working buffer solution (5.5-7.0). On the basis of the results from this screening, a full factorial design was carried out, taking into account only enzyme concentration and Ni/Al molar ratio of the electrosynthesis solution. A full factorial design was performed to study linear interactions between factors and their quadratic effects and the optimal setup was evaluated by the isoresponse curves. The significant factors were: enzyme concentration (linear and quadratic terms) and the interaction between enzyme concentration and Ni/Al molar ratio. Since the major obstacle for application of amperometric glucose biosensors is the interference signal resulting from other electro-oxidizable species present in the real matrices, such as ascorbate (AA), the use of different permselective membranes on Pt-LDHGOx modified electrode was discussed with the aim of improving biosensor selectivity and stability. Conventional membranes obtained using Nafion, glutaraldehyde (GA) vapours, GA-BSA were tested together with more innovative materials like palladium hexacyanoferrate (PdHCF) and titania hydrogels. Particular attention has been devoted to hydrogels, because they possess some attractive features, which are generally considered to favour biosensor materials biocompatibility and, consequently, the functional enzyme stability. The Pt-LDH-GOx-PdHCF hydrogel biosensor presented an anti-interferant ability so that to be applied for an accurate glucose analysis in blood. To further improve the biosensor selectivity, protective membranes containing horseradish peroxidase (HRP) were also investigated with the aim of oxidising the interferants before they reach the electrode surface. In such a case glucose determination was also accomplished in real matrices with high AA content. Furthermore, the application of a LDH containing nickel in the oxidised state was performed not only as a support for the enzyme, but also as anti-interferant sistem. The result is very promising and it could be the starting point for further applications in the field of amperometric biosensors; the study could be extended to other oxidase enzymes.

Analisi della dinamica e composizione chimica del particolato atmosferico mediante un modello alla mesoscala

The vertical profile of aerosol in the planetary boundary layer of the Milan urban area is studied in terms of its development and chemical composition in a high-resolution modelling framework. The period of study spans a week in summer of 2007 (12-18 July), when continuous LIDAR measurements and a limited set of balloon profiles were collected in the frame of the ASI/QUITSAT project. LIDAR observations show a diurnal development of an aerosol plume that lifts early morning surface emissions to the top of the boundary layer, reaching maximum concentration around midday. Mountain breeze from Alps clean the bottom of the aerosol layer, typically leaving a residual layer at around 1500-2000 m which may survive for several days. During the last two days under analysis, a dust layer transported from Sahara reaches the upper layers of Milan area and affects the aerosol vertical distribution in the boundary layer. Simulation from the MM5/CHIMERE modelling system, carried out at 1 km horizontal resolution, qualitatively reproduced the general features of the Milan aerosol layer observed with LIDAR, including the rise and fall of the aersol plume, the residual layer in altitude and the Saharan dust event. The simulation highlighted the importance of nitrates and secondary organics in its composition. Several sensitivity tests showed that main driving factors leading to the dominance of nitrates in the plume are temperature and gas absorption process. A modelling study turn to the analysis of the vertical aerosol profiles distribution and knowledge of the characterization of the PM at a site near the city of Milan is performed using a model system composed by a meteorological model MM5 (V3-6), the mesoscale model from PSU/NCAR and a Chemical Transport Model (CTM) CHIMERE to simulate the vertical aerosol profile. LiDAR continuous observations and balloon profiles collected during two intensive campaigns in summer 2007 and in winter 2008 in the frame of the ASI/QUITSAT project have been used to perform comparisons in order to evaluate the ability of the aerosol chemistry transport model CHIMERE to simulate the aerosols dynamics and compositions in this area. The comparisons of model aerosols with measurements are carried out over a full time period between 12 July 2007 and 18 July 2007. The comparisons demonstrate the ability of the model to reproduce correctly the aerosol vertical distributions and their temporal variability. As detected by the LiDAR, the model during the period considered, predicts a diurnal development of a plume during the morning and a clearing during the afternoon, typically the plume reaches the top of the boundary layer around mid day, in this time CHIMERE produces highest concentrations in the upper levels as detected by LiDAR. The model, moreover can reproduce LiDAR observes enhancement aerosols concentrations above the boundary layer, attributing the phenomena to dust out intrusion. Another important information from the model analysis regard the composition , it predicts that a large part of the plume is composed by nitrate, in particular during 13 and 16 July 2007 , pointing to the model tendency to overestimates the nitrous component in the particular matter vertical structure . Sensitivity study carried out in this work show that there are a combination of different factor which determine the major nitrous composition of the “plume” observed and in particular humidity temperature and the absorption phenomena are the mainly candidate to explain the principal difference in composition simulated in the period object of this study , in particular , the CHIMERE model seems to be mostly sensitive to the absorption process.

Valutazione dello spessore intima-media carotideo come fattore di rischio cardiovascolare nei pazienti affetti da psoriasi moderato-severa

Evaluation of carotid artery intima-media thickness in patients affected by psoriasis Psoriasis is associated with an increased risk of atherosclerosis. This study compared subclinical atherosclerosis, evaluating intima-media thickness the of the carotid in psoriasis vulgaris patients and healthy controls using high-resolution ultrasonography and the correlation of this parameter with other cardiovascular risk factors, like insulin resistance and dyslipidemia, METHODS: We will study 40 psoriasis patients, asymptomatic for cardiovascular diseases, and 40 healthy controls matched for age and sex. Intima-media thickness of the common carotid arteries will be measured ultrasonographically. Diabetes mellitus, hypertension, renal failure, a history of cardiovascular or cerebrovascular disease will be exclusion criteria. Subjects who are receiving lipid-lowering therapy, antihypertensive or anti-aggregant drugs, nitrates or long-term systemic steroids will be also excluded. Objective of this study is the evaluation of carotid artery intima-media thickness and its correlation with other blood cardiovascular risk factors in patients affected by psoriasis but asinptomatic for coronary comparing this data with the healthy control subjects. Considering that the presence of psoriasis is an independent risk factor for subclinical atherosclerosis, we want to consider this method of evaluation of cardiovascular risk and to control this risk to prevent IMA.